From The New York Times:
Mercifully, according to the young science of “heat death,” air moisture is as important as temperature for triggering human mortality, and when thermometers hit 115 degrees Fahrenheit in India and 120 in Pakistan in April, the humidity was quite low. But even so, in parts of India, humidity was still high enough that if the day’s peak moisture had coincided with its peak heat, the combination would have produced “wet-bulb temperatures” — which integrate measures of both into a single figure — already at or past the limit for human survivability. Birds fell dead from the sky.